/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_decimate_q15.c
*
* Description:	Q15 FIR Decimator.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_decimate
 * @{
 */

/**
 * @brief Processing function for the Q15 FIR decimator.
 * @param[in] *S points to an instance of the Q15 FIR decimator structure.
 * @param[in] *pSrc points to the block of input data.
 * @param[out] *pDst points to the location where the output result is written.
 * @param[in] blockSize number of input samples to process per call.
 * @return none.
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
 * Lastly, the accumulator is saturated to yield a result in 1.15 format.
 *
 * \par
 * Refer to the function <code>arm_fir_decimate_fast_q15()</code> for a faster but less precise implementation of this function for Cortex-M3 and Cortex-M4.
 */

#ifndef ARM_MATH_CM0_FAMILY

#ifndef UNALIGNED_SUPPORT_DISABLE

void arm_fir_decimate_q15(
    const arm_fir_decimate_instance_q15 *S,
    q15_t *pSrc,
    q15_t *pDst,
    uint32_t blockSize)
{
    q15_t *pState = S->pState;                     /* State pointer */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q15_t *pStateCurnt;                            /* Points to the current sample of the state */
    q15_t *px;                                     /* Temporary pointer for state buffer */
    q15_t *pb;                                     /* Temporary pointer coefficient buffer */
    q31_t x0, x1, c0, c1;                          /* Temporary variables to hold state and coefficient values */
    q63_t sum0;                                    /* Accumulators */
    q63_t acc0, acc1;
    q15_t *px0, *px1;
    uint32_t blkCntN3;
    uint32_t numTaps = S->numTaps;                 /* Number of taps */
    uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M;  /* Loop counters */


    /* S->pState buffer contains previous frame (numTaps - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (numTaps - 1u);


    /* Total number of output samples to be computed */
    blkCnt = outBlockSize / 2;
    blkCntN3 = outBlockSize - (2 * blkCnt);


    while(blkCnt > 0u)
    {
        /* Copy decimation factor number of new input samples into the state buffer */
        i = 2 * S->M;

        do
        {
            *pStateCurnt++ = *pSrc++;

        }
        while(--i);

        /* Set accumulator to zero */
        acc0 = 0;
        acc1 = 0;

        /* Initialize state pointer */
        px0 = pState;

        px1 = pState + S->M;


        /* Initialize coeff pointer */
        pb = pCoeffs;

        /* Loop unrolling.  Process 4 taps at a time. */
        tapCnt = numTaps >> 2;

        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numTaps-4 coefficients. */
        while(tapCnt > 0u)
        {
            /* Read the Read b[numTaps-1] and b[numTaps-2]  coefficients */
            c0 = *__SIMD32(pb)++;

            /* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
            x0 = *__SIMD32(px0)++;

            x1 = *__SIMD32(px1)++;

            /* Perform the multiply-accumulate */
            acc0 = __SMLALD(x0, c0, acc0);

            acc1 = __SMLALD(x1, c0, acc1);

            /* Read the b[numTaps-3] and b[numTaps-4] coefficient */
            c0 = *__SIMD32(pb)++;

            /* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
            x0 = *__SIMD32(px0)++;

            x1 = *__SIMD32(px1)++;

            /* Perform the multiply-accumulate */
            acc0 = __SMLALD(x0, c0, acc0);

            acc1 = __SMLALD(x1, c0, acc1);

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* If the filter length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = numTaps % 0x4u;

        while(tapCnt > 0u)
        {
            /* Read coefficients */
            c0 = *pb++;

            /* Fetch 1 state variable */
            x0 = *px0++;

            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 = __SMLALD(x0, c0, acc0);
            acc1 = __SMLALD(x1, c0, acc1);

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Advance the state pointer by the decimation factor
         * to process the next group of decimation factor number samples */
        pState = pState + S->M * 2;

        /* Store filter output, smlad returns the values in 2.14 format */
        /* so downsacle by 15 to get output in 1.15 */
        *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
        *pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16));

        /* Decrement the loop counter */
        blkCnt--;
    }



    while(blkCntN3 > 0u)
    {
        /* Copy decimation factor number of new input samples into the state buffer */
        i = S->M;

        do
        {
            *pStateCurnt++ = *pSrc++;

        }
        while(--i);

        /*Set sum to zero */
        sum0 = 0;

        /* Initialize state pointer */
        px = pState;

        /* Initialize coeff pointer */
        pb = pCoeffs;

        /* Loop unrolling.  Process 4 taps at a time. */
        tapCnt = numTaps >> 2;

        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numTaps-4 coefficients. */
        while(tapCnt > 0u)
        {
            /* Read the Read b[numTaps-1] and b[numTaps-2]  coefficients */
            c0 = *__SIMD32(pb)++;

            /* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
            x0 = *__SIMD32(px)++;

            /* Read the b[numTaps-3] and b[numTaps-4] coefficient */
            c1 = *__SIMD32(pb)++;

            /* Perform the multiply-accumulate */
            sum0 = __SMLALD(x0, c0, sum0);

            /* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
            x0 = *__SIMD32(px)++;

            /* Perform the multiply-accumulate */
            sum0 = __SMLALD(x0, c1, sum0);

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* If the filter length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = numTaps % 0x4u;

        while(tapCnt > 0u)
        {
            /* Read coefficients */
            c0 = *pb++;

            /* Fetch 1 state variable */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 = __SMLALD(x0, c0, sum0);

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Advance the state pointer by the decimation factor
         * to process the next group of decimation factor number samples */
        pState = pState + S->M;

        /* Store filter output, smlad returns the values in 2.14 format */
        /* so downsacle by 15 to get output in 1.15 */
        *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));

        /* Decrement the loop counter */
        blkCntN3--;
    }

    /* Processing is complete.
     ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
     ** This prepares the state buffer for the next function call. */

    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;

    i = (numTaps - 1u) >> 2u;

    /* copy data */
    while(i > 0u)
    {
        *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
        *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;

        /* Decrement the loop counter */
        i--;
    }

    i = (numTaps - 1u) % 0x04u;

    /* copy data */
    while(i > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        i--;
    }
}

#else


void arm_fir_decimate_q15(
    const arm_fir_decimate_instance_q15 *S,
    q15_t *pSrc,
    q15_t *pDst,
    uint32_t blockSize)
{
    q15_t *pState = S->pState;                     /* State pointer */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q15_t *pStateCurnt;                            /* Points to the current sample of the state */
    q15_t *px;                                     /* Temporary pointer for state buffer */
    q15_t *pb;                                     /* Temporary pointer coefficient buffer */
    q15_t x0, x1, c0;                              /* Temporary variables to hold state and coefficient values */
    q63_t sum0;                                    /* Accumulators */
    q63_t acc0, acc1;
    q15_t *px0, *px1;
    uint32_t blkCntN3;
    uint32_t numTaps = S->numTaps;                 /* Number of taps */
    uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M;  /* Loop counters */


    /* S->pState buffer contains previous frame (numTaps - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (numTaps - 1u);


    /* Total number of output samples to be computed */
    blkCnt = outBlockSize / 2;
    blkCntN3 = outBlockSize - (2 * blkCnt);

    while(blkCnt > 0u)
    {
        /* Copy decimation factor number of new input samples into the state buffer */
        i = 2 * S->M;

        do
        {
            *pStateCurnt++ = *pSrc++;

        }
        while(--i);

        /* Set accumulator to zero */
        acc0 = 0;
        acc1 = 0;

        /* Initialize state pointer */
        px0 = pState;

        px1 = pState + S->M;


        /* Initialize coeff pointer */
        pb = pCoeffs;

        /* Loop unrolling.  Process 4 taps at a time. */
        tapCnt = numTaps >> 2;

        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numTaps-4 coefficients. */
        while(tapCnt > 0u)
        {
            /* Read the Read b[numTaps-1] coefficients */
            c0 = *pb++;

            /* Read x[n-numTaps-1] for sample 0 and for sample 1 */
            x0 = *px0++;
            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 += x0 * c0;
            acc1 += x1 * c0;

            /* Read the b[numTaps-2] coefficient */
            c0 = *pb++;

            /* Read x[n-numTaps-2] for sample 0 and sample 1 */
            x0 = *px0++;
            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 += x0 * c0;
            acc1 += x1 * c0;

            /* Read the b[numTaps-3] coefficients */
            c0 = *pb++;

            /* Read x[n-numTaps-3] for sample 0 and sample 1 */
            x0 = *px0++;
            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 += x0 * c0;
            acc1 += x1 * c0;

            /* Read the b[numTaps-4] coefficient */
            c0 = *pb++;

            /* Read x[n-numTaps-4] for sample 0 and sample 1 */
            x0 = *px0++;
            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 += x0 * c0;
            acc1 += x1 * c0;

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* If the filter length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = numTaps % 0x4u;

        while(tapCnt > 0u)
        {
            /* Read coefficients */
            c0 = *pb++;

            /* Fetch 1 state variable */
            x0 = *px0++;
            x1 = *px1++;

            /* Perform the multiply-accumulate */
            acc0 += x0 * c0;
            acc1 += x1 * c0;

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Advance the state pointer by the decimation factor
         * to process the next group of decimation factor number samples */
        pState = pState + S->M * 2;

        /* Store filter output, smlad returns the values in 2.14 format */
        /* so downsacle by 15 to get output in 1.15 */

        *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
        *pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16));

        /* Decrement the loop counter */
        blkCnt--;
    }

    while(blkCntN3 > 0u)
    {
        /* Copy decimation factor number of new input samples into the state buffer */
        i = S->M;

        do
        {
            *pStateCurnt++ = *pSrc++;

        }
        while(--i);

        /*Set sum to zero */
        sum0 = 0;

        /* Initialize state pointer */
        px = pState;

        /* Initialize coeff pointer */
        pb = pCoeffs;

        /* Loop unrolling.  Process 4 taps at a time. */
        tapCnt = numTaps >> 2;

        /* Loop over the number of taps.  Unroll by a factor of 4.
         ** Repeat until we've computed numTaps-4 coefficients. */
        while(tapCnt > 0u)
        {
            /* Read the Read b[numTaps-1] coefficients */
            c0 = *pb++;

            /* Read x[n-numTaps-1] and sample */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += x0 * c0;

            /* Read the b[numTaps-2] coefficient */
            c0 = *pb++;

            /* Read x[n-numTaps-2] and  sample */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += x0 * c0;

            /* Read the b[numTaps-3]  coefficients */
            c0 = *pb++;

            /* Read x[n-numTaps-3] sample */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += x0 * c0;

            /* Read the b[numTaps-4] coefficient */
            c0 = *pb++;

            /* Read x[n-numTaps-4] sample */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += x0 * c0;

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* If the filter length is not a multiple of 4, compute the remaining filter taps */
        tapCnt = numTaps % 0x4u;

        while(tapCnt > 0u)
        {
            /* Read coefficients */
            c0 = *pb++;

            /* Fetch 1 state variable */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += x0 * c0;

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Advance the state pointer by the decimation factor
         * to process the next group of decimation factor number samples */
        pState = pState + S->M;

        /* Store filter output, smlad returns the values in 2.14 format */
        /* so downsacle by 15 to get output in 1.15 */
        *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));

        /* Decrement the loop counter */
        blkCntN3--;
    }

    /* Processing is complete.
     ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
     ** This prepares the state buffer for the next function call. */

    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;

    i = (numTaps - 1u) >> 2u;

    /* copy data */
    while(i > 0u)
    {
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        i--;
    }

    i = (numTaps - 1u) % 0x04u;

    /* copy data */
    while(i > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        i--;
    }
}


#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

#else


void arm_fir_decimate_q15(
    const arm_fir_decimate_instance_q15 *S,
    q15_t *pSrc,
    q15_t *pDst,
    uint32_t blockSize)
{
    q15_t *pState = S->pState;                     /* State pointer */
    q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    q15_t *pStateCurnt;                            /* Points to the current sample of the state */
    q15_t *px;                                     /* Temporary pointer for state buffer */
    q15_t *pb;                                     /* Temporary pointer coefficient buffer */
    q31_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
    q63_t sum0;                                    /* Accumulators */
    uint32_t numTaps = S->numTaps;                 /* Number of taps */
    uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M;  /* Loop counters */



    /* Run the below code for Cortex-M0 */

    /* S->pState buffer contains previous frame (numTaps - 1) samples */
    /* pStateCurnt points to the location where the new input data should be written */
    pStateCurnt = S->pState + (numTaps - 1u);

    /* Total number of output samples to be computed */
    blkCnt = outBlockSize;

    while(blkCnt > 0u)
    {
        /* Copy decimation factor number of new input samples into the state buffer */
        i = S->M;

        do
        {
            *pStateCurnt++ = *pSrc++;

        }
        while(--i);

        /*Set sum to zero */
        sum0 = 0;

        /* Initialize state pointer */
        px = pState;

        /* Initialize coeff pointer */
        pb = pCoeffs;

        tapCnt = numTaps;

        while(tapCnt > 0u)
        {
            /* Read coefficients */
            c0 = *pb++;

            /* Fetch 1 state variable */
            x0 = *px++;

            /* Perform the multiply-accumulate */
            sum0 += (q31_t) x0 * c0;

            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Advance the state pointer by the decimation factor
         * to process the next group of decimation factor number samples */
        pState = pState + S->M;

        /*Store filter output , smlad will return the values in 2.14 format */
        /* so downsacle by 15 to get output in 1.15 */
        *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* Processing is complete.
     ** Now copy the last numTaps - 1 samples to the start of the state buffer.
     ** This prepares the state buffer for the next function call. */

    /* Points to the start of the state buffer */
    pStateCurnt = S->pState;

    i = numTaps - 1u;

    /* copy data */
    while(i > 0u)
    {
        *pStateCurnt++ = *pState++;

        /* Decrement the loop counter */
        i--;
    }


}
#endif /*   #ifndef ARM_MATH_CM0_FAMILY */


/**
 * @} end of FIR_decimate group
 */
